The invention relates to a method of manufacturing glass bodies, in which a thixotropic suspension consisting of SiO.sub.2 particles having a diameter in the range from 10 to 500 nm is formed into a green body, purified and sintered.
Such a method of manufacturing highly pure quartz glass tubes is known from DE-OS 35 37 972 (corresponding to U.S. Pat. No. 4,726,828), in which a form-retaining, open-pore green body is manufactured by cross-linking (coagulating) a suspension of colloidal quartz glass particles. After drying and purifying, this green body is sintered into a transparent quartz glass tube. In particular for manufacture, the solids content of the suspension should be as large as possible because the cross-linking time thus decreases substantially and, consequently, the solidified green body can be removed from the moulding equipment sooner.
Such highly filled SiO.sub.2 suspensions are very thioxtropic owing in particular to ionogenic additives, and their manufacture is problematic in practice because a dilatant phase occurs during mixing the microdispersed solids content with the dispersing liquid. This becomes apparent in that the viscosity of the suspension increases as the shear increases. In order to obtain a highly filled suspension which can still be poured readily an intricate method of manufacturing the suspension must be used in which there is little shear during stirring in and much shear during homogenizing. Owing to the rapid solidification of such a highly filled suspension the separation of agglomerated particles or coarse impurities from the suspension also forms a problem.